Racks: Timber painted with tar on which oysters are grown.
Radial symmetry: Having a body structure arranged like spokes radiating out from the centre of a wheel.
Radiation: Sun's rays that are reflected (radiated). Also radiation from nuclear activity
Radioactive: Material that gives out harmful radiation.
Radula: A rough tongue or band of horny teeth used by snails and other molluscs to scrape algae or bore into shells.
Rapids: Rough water caused by moving water over rocks.
Rathbunaster: A deep sea star with many arms that dwells on the seafloor.
Ray: A fish related to sharks and skates, which bears live young and has a cartilaginous skeleton, a broad flat body and a blunt snout.
Raze: To destroy or tear down.
Recreational: Used here to describe fishers who do not sell their catch.
Recycle: To use discarded material for another purpose.
Red snapper: A fish with red sides, popular with people as a food fish. Many red snapper are caught in the Gulf of Mexico. The name "red snapper" is sometimes given to other, unrelated species of fishes, such as Pacific rockfishes.
Reef: An underwater structure; something that extends up from the seafloor but does not rise above the surface of the water like an island. Coral reefs are formed from the hard skeletons of coral. There are also rocky reefs, which are piles of rock under water.
Reference: (noun) a source of information; (verb) to identify and record a source of information.
Refuge: A safe place.
Regulator: In scuba diving, the device used to regulate the amount of air coming from an air tank.
Regurgitated: In birds, to bring back food from the crop to feed young chicks.
Rehabilitate: To restore to health or wholeness.
Relative density: The ratio of a substance to the density of water.
Reproductive cells: Cells that make sperm and eggs.
Research: Scientific study to find out facts, test models and develop theories about the natural world.
Residual: In aquariums, material left behind in the filter.
Resorts: Places where entertainment, accommodation, meals and marine activities take place.
Restoration: Repair and display of maritime artifacts.
Resuscitate: To revive.
Retaliators: Animals that will only attack if accidentally or deliberately disturbed.
Rhizome: An underground horizontal stem, found in seagrass, that functions as a reproductive structure. New shoots develop as the rhizome grows.
Ribbon eel: A fish in the moray eel family, with a long slender body and large feathery nostrils.
Rip: Fast-moving water in surf zone caused by moving sandbanks.
Riparian: Pertaining to the river bank. Riparian vegetation is vegetation along the river.
Rockhopper trawl: A type of trawl net equipped with tires or rollers that let the net roll over rocky areas on the seafloor. Rockhopper trawls are very destructive to the seafloor habitat.
Rookery: Place where seabirds nest in groups.
Root stabilized: Held together or held in place by the roots of plants.
Rostrum: Central, forward-projecting and occasionally long spine between the eyes of crustaceans.
ROV: A remotely operated vehicle that dives in deep water to videotape or collect deep sea animals or other scientific data. An ROV doesn't carry people--it's operated from a research ship at the ocean's surface.
Rowlock: A device on the gunwale of a vessel on which an oar rests or swings.
Rrarranhdarr Dhuludur: Aboriginal term for summer and spring.
Ruddy duck: A species of small duck which lives in coastal areas; males are reddish-brown.
Ruddy turnstone: A shorebird with short legs and a reddish-brown back. Turnstones flip over stones to find small invertebrates to eat.
Rules: (boating) Governmental regulations for preventing collisions on the water.
Runoff: Water that runs from the land or escapes from a pond into a larger body of water.
Rural land use: Land used for farming.